The field of the disclosure relates generally to gas turbine engine rotors and, more particularly, to fuel system interfaces used to prevent rotor over-speed conditions.
Gas turbine engines typically include over-speed protection systems that provide rotor over-speed protection. In known systems, the over-speed protection systems either maintains the rotor speed below critical rotor speeds, or shuts off fuel flow to an engine combustor. One type of known protection system receives signals, indicative of rotor speed, from mechanical speed sensors. The mechanical speed sensors include rotating flyweight sensing systems that indicate an over-speed condition as a result of the rotor rotating above the normal operational maximum speeds. The flyweight sensing systems are hydro-mechanically coupled to a fuel bypass valve that reduces an amount of fuel that can be supplied to the engine if an over-speed condition is sensed.
Other types of known over-speed protection systems receive over-speed signal information from electronic control sensors. Known electronic controls derive over-speed conditions from such electronic control sensors. Such systems provide for rapid fuel shutoff and engine shutdown if engine speed exceeds a normal maximum value.
In some known aircraft, propulsion systems are used to control a flow of exhaust gases for a variety of aircraft functions. For example, such systems can be used to provide thrust for Vertical Take-Off and Landing (VTOL), Short Take-Off Vertical Landing (STOVL) and/or Extreme Short Take-Off and Landing (ESTOL) aircraft. At least some known STOVLs and ESTOLs use vertical thrust posts that facilitate short, and extremely short, take-offs and landings. In aircraft using vertical thrust posts or nozzles, exhaust from a common plenum is channeled to thrust posts during take-off and landing operations, and, at a predetermined altitude, the exhaust is channeled from the common plenum through a series of valves, to a cruise nozzle.
At least some known gas turbine engines include combustion control systems that include symmetric channels for providing electric signals to the control system. However, such channels may allow common design deficiencies in each channel to cause transients during operation of the control system and/or gas turbine engine. For example, at least one such known combustion control system is an over-speed system that protects an airframe and/or a pilot from turbine and/or compressor wheel transients caused by a rotational speed over the design limits of a turbine and/or a compressor. More specifically, when the rotational speed is over a design limit, the over-speed system will shut down the gas turbine engine by preventing fuel from flowing to the engine. As such, the over-speed system can prevent turbine and/or compressor wheel transients from occurring.
However, if the circuitry within full authority digital engine controls (FADECs) that control such an over-speed system have a common design deficiency, both channels of the FADECs may inadvertently command the over-speed system to prevent fuel from flowing to the engine, even though a rotational speed in excess of a design limit has not been reached, causing an unexpected engine shut down. Accordingly, it is desirable to have a combustion control system that will not inadvertently shut down a gas turbine engine when operating conditions are within design limits.